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Estimating the Uncertainty of the Result for Tests of Resistance to Environmental Conditions on the Example of the Method of Resistance to Neutral Salt Mist According to EN ISO 9227 / ASTM B117

Garbacz Marcin

Problemy Kolejnictwa

2023

Z. 198

97--117

Environmental laboratory tests are one of the most frequently performed tests to evaluate materials used, among others, for the construction of rail vehicles. The requirements of the EN ISO/IEC 17025 standard for research laboratories, particularly when evaluating the compliance of materials with the specified requirements, impose on laboratories the need to consider the results of final measurements along with the uncertainties of these results. Due to the complexity of the physical and chemical processes occurring during environmental tests, determining the sources of uncertainty of the measurement result can be very complicated. The article presents one of the methods of estimating the complex uncertainty for environmental tests on the example of corrosion tests using the NORDTEST TR 537 concept of uncertainty estimation. The article presents an exemplary method of uncertainty estimation based on a set of empirical data obtained in an accredited Laboratory for Testing Materials and Structural Elements of the Railway Institute with the use of within-laboratory reproducibility and method bias. Examples of uncertainty estimation depending on the type of tested objects (metal details and paint coatings) and the method of their evaluation after corrosion tests (quantitative and qualitative methods) are presented. The article also briefl y presents the possibilities of interpreting and processing the obtained data as part of the control carried out inside the laboratory on the basis of a simple statistical tool such as Shewhart control charts and the Ishikawa diagram for the method of determining corrosivity in salt chambers, identifying important factors influencing the measurement uncertainty and at the same time showing the complexity the entire research process.

Critical assessment of size exclusion chromatography

Berek D.

Polimery

2004

T. 49, nr 5

313-320

Size exclusion chromatography (SEC) of synthetic polymers is assessed from the point of view of its both strong and weak points, advantages and drawbacks. Basic information on the SEC retention mechanism arc presented together with the complexity of SEC systems and processes. Present stand of SEC instrumentation is outlined and the role of experimental conditions is described. The need of further development of SEC and of standardization of experimental conditions is demonstrated. The enthalpic interactions, leading to adsorption and enthalpic partition phenomena in the SEC columns are described. It is shown that the latter should be suppressed to obtain reliable SEC results. Alternatively, enthalpic interactions can be deliberately combined with the entropic partition (exclusion) basic SEC retention mechanism either to allow separation of complex polymers exhibiting multiple distributions in their molecular characteristics or to increase selectivity of separation.

Oceniono chromatografię żelową (SEC - chromatografia wykluczania wg wymiarów) stosowaną do badań polimerów syntetycznych. Przedstawiono podstawowe informacje o mechaniźmie rozdzielania z uwzględnieniem udziału entropowego i entalpowego. Opisano wpływ wyposażenia, tj. wypełnienia kolumn, fazy ruchomej oraz metod detekcji i typów detektorów, na dokładność metody. Przeanalizowano również wpływ warunków prowadzenia procesu (np. stężenie, objętość nastrzyku, temperatura) na jakość otrzymywanych wyników. Zwrócono uwagę na konieczność normalizacji warunków pomiaru oraz dysponowania doświadczonymi operatorami w celu polepszenia odtwarzalności międzylaboratoryjnej. Wskazano na możliwość poprawy selektywności dzięki zastosowaniu metod złożonych zamiast typowej SEC (np. "enthalpy assisted SEC").